JP3242832B2 - Base film for photographic film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base film for a photographic film, and more particularly to a base film having excellent roll form when the film is wound into a roll, and the flatness of the film caused by the poor form of the roll. The present invention relates to a photographic film base film containing polyethylene-2,6-naphthalenedicarboxylate as a main component, the generation of which is reduced.

[0002]

2. Description of the Related Art Photographic films include those used as roll films such as negative films which are loaded into a general camera and used for photographing, X-ray films, plate making films, and the like.
Some are used as sheet films such as cut films.

A triacetyl cellulose (hereinafter sometimes abbreviated as "TAC") film is mainly used as a base film of the roll-shaped film, and a biaxially stretched polyester made of polyethylene terephthalate is used as a base film of the sheet-like film. Film is mainly used.

A TAC film has no optical anisotropy and high transparency, and has relatively high water absorption as a plastic film. Has an excellent property of being eliminated (curl elimination property) due to rearrangement of molecular chains due to water absorption in the development processing.

[0005] However, with the recent advances in downsizing of photographic devices, it has become necessary to reduce the size of patrones for storing photographic films. In addition, it has been required to have sufficient performance in mechanical strength and dimensional stability even if it is thin. However, when the thickness of the TAC film is reduced, the mechanical strength is insufficient and the demand cannot be satisfied.

On the other hand, biaxially stretched polyethylene terephthalate film has excellent mechanical properties, transparency, dimensional stability,
Despite having heat resistance, chemical resistance, etc., when used in a roll form, it is easy to curl when used in a film and has the ability to make it difficult to curl (hereinafter sometimes referred to as “anti-curling property”) Because of the shortage, it is difficult to use as a base film of a roll film, and as described above, it is used as a sheet film.

[0007] As a method for imparting curl removability to a polyester film, a method of subjecting the film to a heat treatment at a temperature equal to or lower than the glass transition point (Tg) of the polyester is known. However, even the biaxially stretched polyethylene terephthalate film subjected to the heat treatment is insufficient in the curl resolving property.

When the polyester film has poor slipperiness, if the film is wound into a roll as it is, blocking occurs between the films, making it impossible to wind the film. Disadvantages occur frequently. As a method of improving the winding property, a technique of embossing both side edges of the film is known. However, as a result of the study of the present inventors, there may be a difference in the height of each adjacent emboss applied to the film, and if this difference is large,
When the film is wound into a roll, the flatness is deteriorated due to twisting and wrinkling of the film. Further, in this state (wound on a roll) (Tg-40) ° C
When the heat treatment is carried out at a temperature of from Tg to Tg, the deterioration of the flatness becomes more remarkable, and when the flatness of the base film deteriorates, it becomes a cause of application unevenness in the subsequent application of the photosensitive material. It became clear.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a good roll form when a film is wound into a roll and to reduce the occurrence of poor flatness of the film caused by poor roll form. Polyethylene-2,
It is an object of the present invention to provide a photographic film base film containing 6-naphthalenedicarboxylate as a main component.

[0010]

An object of the present invention, in order to solve the problems], according to the present invention, the film both side ends or the both side end portions embossed on one place or more of the intermediate portion, the average particle size
0.1 to 0.8 μm of inorganic fine particles of 0.002 to 0.0
A biaxially stretched polyethylene-2,6-naphthalenedicarboxylate film containing 5% by weight and having a thickness of 40 to 120 µm, having an embossing height of 5 to 40 µm and a lengthwise direction (MD) of the film. The difference between the heights of two or more embosses on a straight line that intersects at right angles
This is achieved by a base film for a photographic film, which is characterized by having a thickness of 5 μm or less.

The biaxially stretched polyethylene according to the present invention
The 2,6-naphthalenedicarboxylate film has a thickness in the range of 40 to 120 μm, preferably 50 to 100 μm.
m. When the thickness is less than 40 μm, the mechanical strength becomes insufficient, or the bending strength of the film decreases, so that when the film is wound around a roll after the film is formed, the deflection of the film becomes large, and the roll form deteriorates. Not preferred. On the other hand, if the thickness exceeds 120 μm, it is not preferable because the meaning of thinning the film is lost.

The biaxially stretched polyethylene-2,6-naphthalenedicarboxylate film is further embossed on both side edges of the film or at one or more locations on both side edges and an intermediate portion thereof. This embossing is performed continuously in the longitudinal direction of the film (MD direction). The embossing process may be performed only on both ends of the film, or on the intermediate portion other than both ends, as long as care is taken not to hinder the undercoating process or emulsion coating on the base film. There can be any number of places. The method of embossing is not particularly limited as long as it is a method of providing continuous irregularities by embossing or the like in the longitudinal direction (MD direction) of the film.
4 and the like can be used.

The height of the emboss in the present invention is 5 to 40.
μm, and more preferably 10 to 30 μm.
If the film is wound without embossing, or if the emboss height is lower than 5 μm,
In addition to blocking between films and rubbing between films, fine scratches are generated, and when heat treatment of a roll-shaped film, flatness due to blocking due to blocking due to tightness of winding and transfer of core occurs, so flat surface for photographic film Sex becomes unsatisfactory. On the other hand, when the height of the emboss exceeds 40 μm, these problems do not occur, but the roll appearance itself becomes unstable, and the roll shifts during roll winding, the roll deformation during roll conveyance, and the roll heat treatment. Deformation due to tight tightening of
Not preferred.

Further, the embossing is performed in the longitudinal direction of the film (M
D) The difference between the heights of two or more embosses existing on a straight line perpendicular to the direction is 5 μm or less. If the difference between the heights of the embosses exceeds 5 μm, the film is undesirably twisted and wrinkled when the film is wound up in a roll, and the flatness of the film is deteriorated. Further, when the roll is heat-treated at a temperature of glass transition point (Tg) to (Tg-40) ° C. of polyethylene-2,6-naphthalenedicarboxylate in a state in which the roll form is bad, the film at each part of the roll becomes unsatisfactory. Since the winding is uniformly performed, the deterioration of the flatness becomes more remarkable, which is not preferable.

The biaxially stretched polyethylene according to the present invention
When the film is held at 110 ° C. for 24 hours, the 2,6-naphthalenedicarboxylate film has a heat shrinkage in the film longitudinal direction (MD direction) of 0.25% or less, and a width of this heat shrinkage. The difference between the maximum value and the minimum value in the direction (MD heat shrinkage (maximum) -MD heat shrinkage (minimum)) is preferably 0.10% or less. 110
When the heat shrinkage in the longitudinal direction of the film when held at 24 ° C. for 24 hours exceeds 0.25%, for example, when a heat treatment at Tg or less is performed during the film conveyance, the film rubs against the film conveyance roll, and fine When scratches are generated and the heat treatment at Tg or less is performed in the state of a wound roll,
Unsatisfactory flatness due to adhesion and rubbing between the films occurs. On the other hand, variations in the heat shrinkage in the film longitudinal direction (MD) in the film width direction when held at 110 ° C. for 24 hours (difference between the maximum value and the minimum value of the heat shrinkage)
Is more than 0.10%, the film sags during the heat treatment at Tg or less, and thereafter, when the film is wound up, adhesion and rubbing of the films occur to deteriorate the flatness of the film. Is not preferred.

The heat shrinkage in the longitudinal direction of the film when held at 110 ° C. for 24 hours is 0.25% or less, and the variation of the heat shrinkage in the film width direction is 0.1% or less. As a method for, for example, biaxially stretched, until the film is wound around the roll after heat setting, to transport the film on the heating transport roll, a method of reducing the speed of the transport roll after the heating transport roll, A method of heating with an IR heater between two conveying rolls having different speeds, a method of cutting off both ends of a film in the middle of a heat setting zone after transverse stretching, and reducing a take-off speed with respect to a film feeding speed, heat setting. After transporting the film over the nozzle that blows out hot air, a method in which the take-up speed is slower than the supply speed, or after winding with a film forming machine, the Tg A method in which the film is transported on the heating transporting roll before the processing is performed, and the speed of the transporting roll is reduced, or the roll speed after the heating zone is increased before the heating zone while transporting the heating zone in the heating oven or the IR heater. , Etc., and any of these methods may be used. In addition, the present invention is not limited to the above-mentioned heat shrinkage rate range, and a low heat yielding treatment as long as the heat shrinkage rate in the longitudinal direction of the film falls within the range of variation in the film width direction. Absent.

The biaxially stretched polyethylene according to the present invention
The 2,6-naphthalenedicarboxylate film preferably has a heat shrinkage in the film width direction (TD direction) of 0.25% or less when the film is kept at 110 ° C. for 24 hours. The heat shrinkage can be reduced during the above-described process of reducing the heat shrinkage in the longitudinal direction of the film or by this method.

Biaxially stretched polyethylene according to the present invention
The 2,6-naphthalenedicarboxylate film further has a degree of film-to-film stiffness of a portion not subjected to embossing of preferably 3 or less, more preferably 2.5 or less, particularly preferably 2 or less. Grade or lower. The higher the grade of the degree of the sharpness, the more difficult the film is to slip, and the smaller the grade, the more the films tend to slip. If the degree of stiffness is higher than the third class, slippage between the films is poor, blocking between the films occurs, generation of scratches by a transport roll or the like during film running,
It is not preferable for use as a photographic film, such that bumps are likely to be formed on the roll when the roll is wound up.

Biaxially stretched polyethylene according to the present invention
The 2,6-naphthalenedicarboxylate film preferably further has a property of hardly curling, that is, an anti-curling property. For example, the anti-curling property at 80 ° C. is 50 [m ⁻¹ ] or less in ANSI curl value. It is preferred that This 80 ° C. is a rough approximation of the highest temperature to which a photographic film is usually exposed in daily life. If the ANSI curl value is larger than 50 [m ^-1 ], it becomes difficult to handle the photo in the developing process, which is not preferable.

Conventionally, evaluation of curling of a photographic film is as follows.
It depends on the extent to which the curl is eliminated through a normal photographic film development or drying step, but if the photographic film base film has the above ANSI curl value, the curl is hard to be formed. It has excellent properties, that is, excellent anti-curling properties, and also has excellent curling-removing properties, in which curling once formed is easily eliminated.

The above ANSI curl value can be given, for example, by heat-treating a roll film at a temperature of (Tg-40) ° C. to Tg. The time of this heat treatment is preferably 0.1 to 1500 hours in terms of production efficiency. If the heat treatment temperature is lower than (Tg-40) ° C., it takes an extremely long time for the heat treatment, and the production efficiency deteriorates, which is not preferable. On the other hand, when the heat treatment temperature exceeds Tg, the anti-curling property becomes inferior (the curl tends to be formed).

The biaxially stretched polyethylene according to the present invention
The 2,6-naphthalenedicarboxylate film contains polyethylene-2,6-naphthalenedicarboxylate as a substantial material, and the polyethylene-2,6-naphthalenedicarboxylate contains ethylene-2,6-naphthalenedicarboxylate. A homopolymer having 6-naphthalene dicarboxylate as all repeating units or a copolymer in which at least 97% of all repeating units are ethylene-2,6-naphthalenedicarboxylate are preferably used.
When the proportion of the ethylene-2,6-naphthalenedicarboxylate unit is 97% or more of all the repeating units, the anti-curling property becomes good, and it is particularly preferable that it is 98% or more.

As the copolymerization component constituting the copolymer, a compound having two ester-forming functional groups in the molecule can be used. For example, oxalic acid, adipic acid,
Dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, 2,7-naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid; oxycarboxylic acids such as p-oxybenzoic acid, p-oxyethoxybenzoic acid; Dihydric alcohols such as methylene glycol, tetramethylene glycol, hexamethylene glycol, cyclohexane dimethylene alcohol, neopentyl glycol, diethylene glycol and the like can be preferably used.

The polyethylene-2,6-naphthalenedicarboxylate is obtained by blocking some or all of the terminal hydroxyl groups and / or carboxyl groups with a monofunctional compound such as benzoic acid or methoxypolyalkylene glycol. Alternatively, it may be one obtained by copolymerizing a very small amount of a trifunctional or higher ester-forming compound such as glycerin or pentaerythritol within a range where a substantially linear polymer can be obtained.

The polyethylene-2,6-naphthalenedicarboxylate may optionally contain additives such as stabilizers, lubricants, ultraviolet absorbers, flame retardants, and dyes.

[0026] In order to impart slipperiness to the film, Ru is small proportion contain inert fine particles. Examples of such inert fine particles include spherical silica, calcium carbonate, alumina, titanium dioxide, kaolin, clay, barium sulfate,
It can be mentioned, such as inorganic particles child of zeolite. Inorganic particles are more natural than natural products due to their uniform particle size.
It is preferably a synthetic product, and any crystalline form of inorganic particles can be used.

[0027] The flat Hitoshitsubu径above kina machine particles 0.1 to 0.8
range der of μm is, it is good <br/> preferable is 0.2 to 0.5 [mu] m.

If the average particle size of the inert fine particles is excessively small, the effect of improving the film's slipperiness, abrasion resistance or winding property is small, while if the average particle size is excessively large, the transparency of the film decreases. Is not preferred.

[0029] The content of the non-machine particles, 0.001 to 0.1
Ri wt% der, it is 0.002% by weight
But good Masui. The amount of addition of the inert fine particles is excessively small.
And the film is likely to slip resistance becomes insufficient, on the other hand over
If the amount is too high, the film haze increases and the transparency becomes insufficient, which is not preferable.

The timing of adding the inert fine particles is not particularly limited as long as it is a stage before the formation of polyethylene-2,6-naphthalenedicarboxylate. For example, the inert fine particles may be added at the polymerization stage. It may be added at the time.

The refractive index of a polyester film is generally higher than that of a photosensitive material or air. For this reason,
When a polyester film is used as the base film of a photographic film, light entering from the edge of the base film is easily reflected at the interface between the film and the photosensitive agent layer, and is also easily reflected at the interface between the film and the atmosphere. The photosensitive layer reaches a part of the photosensitive agent layer away from the light-sensitive layer, and is liable to cause a so-called light piping phenomenon (fog). In order to prevent such a phenomenon, it is preferable to include a dye in the film. As the dye, a dye having excellent heat resistance at the film forming temperature and excellent compatibility with polyester is preferable. In view of the above, a dye having an anthraquinone skeleton is particularly preferable because of excellent heat resistance and compatibility. When the color density is measured in the visible light region using an optical densitometer manufactured by X-Rite, the staining density is at least 0.0
It is preferably from 3 to 0.17. If the color density is lower than 0.03, the effect of preventing the light piping phenomenon is insufficient, which is not preferable. On the other hand, if the color density is higher than 0.17, transparency as a photographic film base film is lost, which is not preferable.

The biaxially stretched polyethylene according to the present invention
The 2,6-naphthalenedicarboxylate film can be produced by a conventionally known method or conditions accumulated in the art.

For example, biaxially stretched polyethylene-2,6-
The naphthalene dicarboxylate film can be advantageously produced by biaxially stretching an unstretched film obtained by a usual method, heat-setting, and then performing a relaxation treatment. More specifically, the unstretched film is 2.0 to 5.0 times in the longitudinal and transverse directions at a glass transition point (Tg) to (Tg + 60) ° C. of polyethylene-2,6-naphthalenedicarboxylate, respectively. (Tg + 50) ° C. to (Tg + 140) ° C. after biaxial stretching at a stretching ratio of
And heat set for 1 to 100 seconds. Regarding the biaxial stretching method, the film may be stretched in the longitudinal direction and then stretched in the transverse direction, or may be stretched in the transverse direction and then stretched in the longitudinal direction. Furthermore, three-stage stretching (for example, vertical, horizontal, vertical, etc.), four-stage stretching (vertical, horizontal,
(Longitudinal, horizontal, etc.), or biaxial stretching in the vertical and horizontal directions simultaneously. Thereafter, the film is subjected to a relaxation treatment until it is wound on a roll. As the relaxation treatment method, for example, a method in which both ends of the film are cut off in the middle of the heat setting zone, and at a temperature equal to or higher than the melting temperature of the film and lower than the melting temperature, the take-off speed is reduced with respect to the film supply speed,
A method of heating with an IR heater between two transport rolls having different speeds, reducing the speed of the transport roll after heating, transporting the film onto the heated transport roll, and reducing the speed of the transport roll after the heat transport roll. Method, a method in which the film is conveyed over a nozzle that blows out hot air after heat setting, and the take-up speed is slower than the supply speed,
Alternatively, after winding with a film forming machine, Tg to (Tg-40)
A method in which the film is transported on a heating transporting roll until the heat treatment is performed at a temperature of 0 ° C, and the speed of the transporting roll is reduced, or the roll speed after the heating zone is transported in a heating oven or a heating zone by an IR heater. There is a method in which the speed is reduced from the roll speed before the heating zone, and any method may be used. The relaxation process is performed by setting the speed reduction rate of the take-up side speed to the supply side speed to 0.1 to 10%. . Further, the present invention is not limited to these methods as long as the method is such that the heat shrinkage in the above-described range and the heat shrinkage in the film longitudinal direction fall within the range of variation in the film width direction.

[0034]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The film properties were measured or evaluated by the following methods.

(1) Thermal shrinkage ratio The sample is kept in hot air at 110 ° C. for 24 hours, and the dimensional change before and after this is determined by the following equation.

(Equation 1) Here, L ₀ is the distance between gauge points before heat shrinkage, and L ₀
Is the distance between gauge points after thermal contraction.

(2) Degree of Hardness A rubber plate is laid on a flat table, and two films containing no dust, dirt, etc. are placed between the films. A cylindrical weight having an outer diameter of 70 mm and a weight of 10 kg is gently placed on the film from directly above, and after 10 minutes, the weight is gently removed. After leaving for 30 seconds, the contact pattern in the circle of the cylinder trace was photographed and the ratio of the area of the shearing portion was measured.
It is rated from 0 to 5 grade.

[0037]

[Table 1]

(3) Anti-curling property (ANSI curl value) A sample film having a size of 120 mm × 35 mm was prepared by
Wound around a 7 mm diameter core, temporarily fixed so as not to unwind, heated at 80 ° C for 2 hours, released from the core,
Immerse in distilled water at 40 ° C. for 15 minutes. Next, a load of 33 g is applied, and the sample is suspended vertically and heat-treated at 55 ° C. for 3 minutes. Sample with curls remaining
The measurement is carried out according to the test method A of SI PH 1.29-1971, and the curl value is calculated by changing inches to metric system.

(4) Ratio of ethylene-2,6-naphthalenedicarboxylate unit The film sample was measured with a solvent (CDCl ₃ : CF ₃ COO).
(D = 1: 1), and ¹ H-NMR measurement is carried out, and it is calculated by the integration ratio of each obtained signal.

(5) Emboss Height The total thickness (t ₁ ) of the film including the embossed irregularities and the film thickness (t ₀ ) of the unembossed portion near the embossed irregularities. The emboss height is calculated based on the difference.

## EQU2 ## Emboss height (μm) = t ₁ −t ₀

(6) Flatness after heat treatment After heat treatment of the film, the flatness of the film (wrinkles, transfer, scratches due to rubbing, poor flatness due to film sticking, poor flatness due to roll deformation) is evaluated in three steps. I do. ：: Good △: Usable (partly defective)
×: Cannot be used

(7) Glass transition point (Tg) Differential scanning calorimeter DSC manufactured by Seiko Denshi Kogyo KK
The measurement is carried out under the following conditions using the sample No. 220. Heating rate: 20 ° C / min Sample amount: 10 mg Measured in a nitrogen stream. The sample is heated and melted under the above conditions, rapidly cooled, and measured again under the above conditions.

Example 1 Polyethylene-2,6-naphthalenedicarboxy containing 0.005% by weight of silica particles having an average particle diameter of 0.3 μm, 0.015% by weight of a dye, and having an intrinsic viscosity of 0.60. The rate was melt-extruded from a die slit and cooled and solidified on a casting drum to produce an unstretched film.

This unstretched film is 3.0 times in the machine direction (MD) and 3.0 in the machine direction (TD).
It was biaxially stretched three times sequentially and heat-fixed to obtain a biaxially oriented film having a thickness of 75 μm. After the heat setting, the film was conveyed onto the heating and conveying roll, the speed of the conveying roll after the heating and conveying roll was reduced, and processing was performed on both ends of the biaxially oriented film so that the height of the embossment was 25 μm. Thereafter, the biaxially oriented film was wound up on a roll. The difference in the height of each emboss present on a straight line intersecting at right angles to the film longitudinal direction (MD) was 3 μm. When the obtained biaxially oriented film was kept at 110 ° C. for 24 hours, the heat shrinkage was 0.20%, and the variation in the heat shrinkage in the film longitudinal direction (MD) in the film width direction was 0%. 0.05%.

From the obtained biaxially oriented film, a width of 1000
A film having a length of 2,000 m and a length of 2,000 mm was sampled and wound around a core having a diameter of 165 mm to form a sample roll. In this state, the temperature was raised to 100 ° C. over 24 hours, kept at 100 ° C. for 24 hours, and then subjected to a heat treatment of cooling to room temperature over 24 hours to obtain a biaxially oriented film having a thickness of 75 μm.

Before and after heat treatment of the biaxially oriented film, the flatness of the film (wrinkles, transfer, presence / absence of poor flatness due to roll deformation) was confirmed. Table 2 shows the physical properties of the film before the heat treatment and the flatness of the film after the heat treatment.

Example 2 A film was formed in the same manner as in Example 1 except that the height of the emboss was 5 μm and the film was wound. Table 2 shows the results.

Example 3 A film was formed in the same manner as in Example 1 except that the height of the emboss was 40 μm and the film was wound. Table 2 shows the results.

[0049]

Example 4 A film was formed in the same manner as in Example 1 except that the film was wound by embossing and winding the film at both ends and two centers. Table 2 shows the results.

[Example 5 ] A film was formed in the same manner as in Example 1 except that the heat shrinkage after leaving at 110 ° C for 24 hours was 0.25%.
Table 2 shows the results.

Example 6 The same procedure as in Example 1 was carried out except that the range of the thermal shrinkage in the MD (longitudinal direction) of the film in the width direction when left at 110 ° C. for 24 hours was 0.10%. Was formed. Table 2 shows the results.

Comparative Example 1 A film was formed in the same manner as in Example 1, except that the height of the emboss was changed to 50 μm. Table 2 shows the results.

Comparative Example 2 A film was formed in the same manner as in Example 1, except that the height of the emboss was 3 μm and the difference in the height of the emboss was 1 μm. Table 2 shows the results.

Comparative Example 3 A film was formed in the same manner as in Example 1, except that the difference in emboss height was changed to 14 μm.
Table 2 shows the results.

Comparative Example 4 A film was formed in the same manner as in Example 1 except that the thickness of the film was changed to 30 μm. Table 2 shows the results.

[0057]

[Table 2]

[0058]

According to the present invention, polyethylene-2 having a good roll form when the film is wound into a roll and reducing the occurrence of poor flatness of the film caused by the poor form of the roll. And a 6-naphthalenedicarboxylate as a main component.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-253638 (JP, A) JP-A-8-278594 (JP, A) JP-A-7-281356 (JP, A) Official skill number 94-6023 (58) Fields investigated (Int.Cl. ⁷ , DB name) G03C 1/765 G03C 1/795

Claims (4)

(57) [Claims] To 1. A film both side ends, or the both side end portions embossed on one place or more of the intermediate portion, a flat
Inorganic fine particles having an average particle size of 0.1 to 0.8 μm
A biaxially stretched polyethylene-2,6-naphthalenedicarboxylate film containing 0.05% by weight and having a thickness of 40 to 120 µm, and having an emboss height of 5 to 40 µm.
And a height difference between two or more embosses present on a straight line intersecting at right angles to the longitudinal direction (MD) of the film is 5 μm or less. 2. The film has a heat shrinkage in the longitudinal direction of 0.25% when held at 110 ° C. for 24 hours.
And the difference between the maximum value and the minimum value of the heat shrinkage in the film width direction (MD heat shrinkage (maximum) −MD
2. The photographic film base film according to claim 1, wherein the heat shrinkage (minimum) is 0.10% or less. 3. The heat shrinkage in the film width direction (TD) when the film is held at 110 ° C. for 24 hours is 0.1 mm.
The photographic film base film according to claim 1, wherein the content is 25% or less. 4. The photographic film according to claim 1, wherein in the polyethylene-2,6-naphthalenedicarboxylate, the ethylene-2,6-naphthalenedicarboxylate unit accounts for at least 97% of the total repeating units. Base film.